Electrostatic image development

ABSTRACT

A PROCESS IN WHICH AN ELECTROSTATIC IMAGE-BEARING INSULATING SHEET IS BROUGHT INTO CONTACT WITH A COVER SHEET BY A PAIR OF ROLLS FORMING A LINE OF CONTACT AT WHICH THE DEVELOPMENT TAKES PLACE. A BEAD OF LIQUID DEVELOPER IS PLACED BETWEEN THE SHEETS AND AS THE SHEETS ARE MOVED AS A UNIT BETWEEN THE ROLLS, THE BEAD IS WIPED ACROSS THE SHEET AND IMAGES ARE DEVELOPED IN ACCORDANCE WITH THE POTENTIAL APPLIED TO THE ROLL IN CONTACT WITH ITS RESPECTIVE SHEET. THE PROCESS INCLUDES THE FOLLOWING EMBODIMENTS: THE ELECTROSTATIC IMAGE INDUCED ON THE COVER SHEET CAN BE DEVELOPED; THE ELECTROSTATIC IMAGE ON THE INSULATING SHEET CAN BE DEVELOPED WITH SIMULTANEOIUS TRANSFER OF THE DEVELOPER PARTICLES TO THE COVER SHEET; THE ELECTROSTATIC IMAGE ON THE INSULATING SHEET CAN BE DEVELOPED AND SIMULTANEOUS PHYSICALLY TRANSFERRING THE TONER PARTICLES TO THE COVER SHEET; AND THE ELECTROSTATIC IMAGE ON THE INSULATING LAYER CAN BE DEVELOPED WITH SIMULTANEOUS DEVELOPMENT OF THE ELECTROSTATIC IMAGE INDUCED ON THE COVER SHEET.

' Jan. 19,. 1971 G, H, ,ROBINSON T A1. 3,556,784`

vELECIROS'IA'IIC IMAGE DEVELOPMENT Original Filed July 24, 1963' GENE HROB/NS/V JAMES G. JPV/S A TTOR/VEYS United States Patent O 3,556,784ELECTROSTATIC IMAGE DEVELOPMENT Gene H. Robinson and James G. Jarvis,Rochester, N.Y.,

assignors to Eastman Kodak Company, Rochester, N.Y,

a corporation of New Jersey Continuation of application Ser. No.297,263, July 24,

1963. This application Sept. 21, 1966, Ser. No. 581,116 Int. Cl. G03g13/16, 13/10, 15/10 U.S. Cl. 96-1.4 14 Claims ABSTRACT OF THE DISCLOSUREA process in which an electrostatic image-bearing insulating sheet isbrought into contact with a cover sheet by a pair of rolls forming aline of contact at which the development takes place. A bead of liquiddeveloper is placed between the sheets and as the sheets are moved as aunit between the rolls, the bead is wiped across the sheet and imagesare developed in accordance with the potential applied-to the roll incontact with its 'respective sheet. The process includes the followingembodiments: the electrostatic image induced on the cover sheet can bedeveloped; the electrostatic image on the insulating sheet can bedeveloped with simultaneous transfer of the developer particles to thecover sheet; the electrostatic image on the insulating sheet can bedeveloped and simultaneous physically transferring the toner particlesto the cover sheet; and the electrostatic image on the insulating layercan be developed with simultaneous development of the electrostaticimage induced on the cover sheet.

This application is a continuation of copending application Ser. No.297,263, filed July 24, 1963, and now abandoned.

This invention relates to electrostatic printing and more particularlyto improved processes employing liquid developers for convertingelectrostatic images into positive prints.

Processes for forming an electrostatic image on an insulating sheet arewell known, for example, by xerography. Processes employing liquiddevelopers for subsequently converting such electrostatic images intovisual records are also well known. Such liquid developers comprise anely divided solid or toner dispersed in a liquid having a highelectrical resistance. The liquid developer is applied to the sheetcarrying the electrostatic image by immersion of the sheet in the liquiddeveloper or by owing the liquid developer over the sheet.

However, in all such processes a layer of the suspending liquid from theliquid developer is left on the electrostatic image-bearing sheet alongwith the toner particles. The presence of this layer of the suspendingliquid is undesirable from several standpoints. That part which remainsin the non-image areas with some suspended toner may produce backgroundfog as the solvent is evaporated; fortunately, this is not too serious aproblem, but in any case the present invention corrects it. A moreserious trouble arises from the liquid which stays in the image areasalong with the desired toner particles. This liquid tends to hinder thetransfer of the toner particles to a permanent record media. If thepermanent record rnedium is absorbent, too much of the suspending liquidis absorbed thereby without a sufficient quantity of the toner particlesbeing transferred. If the permanent record medium is not absorbent, thepressure that is applied between the two layers produces a flood of thesuspending liquid which tends to wash the toner particles otf of theimage areas of the insulating sheet.

Further, such processes require a relatively large quantity of liquiddeveloper. This is disadvantageous both economically and safetywise. Thesuspending liquid is sometimes ilammable or toxic and it is most oftenvolatile.

Still further, if an immediate visual inspection of the image isdesired, and if the print must be handled, time is consumed whileWaiting for the layer of suspending liquid to evaporate.

It is an object of the present invention to provide a process fordeveloping an electrostatic image employing a minimum quantity of liquiddeveloper.

It is another object of the present invention to develop electrostaticimages with liquid developer Without permitting any appreciable layer ofthe suspending liquid to deposit on the image-bearing sheet, in eitherthe nonimage areas or the image areas.

It is an incidental object of the invention that it permits theA use ofsuspending liquids which are less volatile, which in turn reduces thedangers of fire and toxicity, and extends the choice of suspendingliquids.

It is an object of one embodiment of the present invention to providesimultaneous development and transfer in one step instead of two or moresteps.

It is a further object of such embodiment of the invention to providefor the simultaneous formation of a positive print on the receivingsheet and a reverse-reading negative print on the recording layer, or areverse of this, by the proper selection of materials.

It is a still further object of the present invention to provide for theformation of a right-reading print or, if desired, a wrong-reading print(for example, for use in xeroprinting plates) by ree'x, contact, orprojection printing of a negative or a positive, by proper choice ofcharged toner particles, proper transfer paper, and proper voltages.Such versatility is not only available but is convenient with thepresent invention.

These obejcts are accomplished by the invention in all of itsembodiments by wiping an electrostatic image with a bead of liquiddeveloper. This is strictly a wiping action in which the bead reaches anarea of the image and immediately thereafter is wiped olf; it is not aspreading action. Simple spreading would have little or no advantageover immersion or ilowing of the developer over the image.

The preferred method according to the invention of providing such highlydesirable wiping action employs two rollers or their equivalents tobring the electrostatic imagebearing insulating sheet into contact witha cover sheet, between which sheets, adjacent the line of contact, ispositioned a bead or pod of liquid developer. The sheets are thensqueezed between the rollers, wiping the bead across both sheets, andsuiicient pressure is applied so that substantially no liquid gets pastthe rollers. Toner is deposited and liquid is wiped off in oneoperation. The process includes the following different preferredembodiments:

(l) A process for developing an electrostatic image induced on the coversheet,

(2) A process for developing an electrostatic image on the insulatingsheet and simultaneously transferring the developer particles to thecover sheet which contains a resin layer softened by a carrier liquid,e.g., cyclohexane in the liquid developer,

(3) A process for developing an electrostatic image on the insulatingsheet and simultaneously physically transferring the toner particles tothe cover sheet, and

(4) A process for developing an electrostatic image on the insulatinglayer and simultaneously developing an electrostatic image induced onthe cover sheet.

Each of the above species of the invention has certain advantages inaddition to those stated above. In each of the above species of theinvention a direct print is produced. It is desirable to have such achoice of processes, because it is sometimes necessary to reproduce froma negative and sometimes from a positive document and because a choiceof reflex, projection, or contact exposures is often desirable. It is anobject of the invention to provide positive, right-reading printsregardless of the nature of the document to be reproduced and thedesired type of exposure,

An essential feature of the invention is that as the electrostaticimage-bearing sheet and the cover sheet are brought into contact,sufficient pressure is applied so that substantially none of thesuspending liquid passes beyond the line of contact. There is nospreading of a liquid layer as is required in diffusion transferprocessing of silver halide photographic films, and as is commonly usedin cameras with built-in processing. According to the present inventiona narrow bead of liquid developer moves across the image, leavingnothing noticeable except the imagewise distributed toner particles.Development (and/ or transfer) is complete at the rollers.

While it may be true that a minute quantity of the suspending liquidmust theoretically get past the line of contact, such quantity is soinappreciable that it is not noticeable. The liquid is eitherimmediately absorbed by the sheets or immediately evaporated uponseparation of the sheets without leaving any apparent residue. That is,if there is any developer (liquid plus toner) left after the wipingaction, it is so small that the toner is invisible, i.e., notnoticeable. When the solvent is gone, by absorption or evaporation,there is no toner visible. As a practical matter there is effectively noliquid left and no toner left except in the image areas.

The above-mentioned different species are provided by varying thepolarity of charge on the toner particles, the type of cover paper andthe type of susupending liquid in the liquid developer, and the use andamount ofpotential applied to the transfer sheet and to theelectrostatic image-bearing sheet.

The present invention will be more fully understood from the followingdetailed description of iive examples described with reference to theaccompanying drawing in which:

FIGS. 1-5 are diagrammatic views through a xerographic sheet, a coversheet, a bead of liquid developer, and a set of rollers, showing theposition of electrical charges during the processes of Examples 1-5 ofthe present invention, and

FIG. 6 is a diagrammatic view of a pod of liquid developer attached to asheet of electrostatic printing material.

The present invention will be described in detail by way of Examples1-5, which correspond to FIGS. 1-5. These examples will be limited to axerographically produced electrostatic image. Some of the advantages ofthe invention are directed particularly thereto, i.e., those advantagesconcerned with the production of a positive print regardless of thenature of the document to be reproduced (negative or positive) andwhether the desired type of exposure is reflex, projection, or contact.However, the remaining advantages of the invention are not limitedthereto. An electrostatic image can be produced on an insulating sheetby other than the use of a photoconductive insulating sheet as used inxerography. And such electrostatic images can be developed by theprocess of the present invention to achieve the advantages inherent inthis process as discussed above.

EXAMPLE NO. 1

FIG. l shows a simultaneous positive-positive development andtransfer'process. The term positive-positive means that the document tobe reproduced is a positive and that the print produced by the processis also a positive. This embodiment of the invention is directed to theproduction of a positive print from a positive transparency byprojection exposure. A zinc-oxide-in-resin-binder xerographic sheet 10(4 in. x l1 in.) bearing a negatively charged wrong-readingelectrostatic image 11 is brought into contact with a clay-coated paperreceiving sheet 12 (4 in. x 11 in.) by means of two grounded conductiverollers 14 and 16. The rollers 14 and 16 are mounted to rotate in thedirection indicated by the arrows. A bead 18 of liquid developercontaining about 10 ml. of a negative toner developer is positionedbetween the two sheets as shown in FIG. l. The developer was made bydispersing about 0.1 g. Sherwin-Williams Solefast green lithographic inkin about ml. of cyclohexane. A positive electrostatic image 13 isinduced on the receiving sheet 12. FIG. 1 exaggerates the production ofthe induced charge on the receiving sheet. The induced charge isobtained when the two sheets are brought into close proximity. This isalso true for the subsequent figures described below. The negativelycharged toner particles are attracted to the positive electrostaticimage 13 on the receiving sheet 12 to produce a right-reading positiveprint thereon.

The receiving sheet in this embodiment and the following embodiments canbe any type of paper, preferably absorptive. Conductive material, suchas metal foil and the like, can also be used.

The bead 18 in this embodiment of the invention as well as in all of thefollowing embodiments can be replaced with a pod made from, for example,a photographic dry mounting tissue rolled into cylindrical form and heatsealed at the ends. Other materials which can be used for making podsinclude an aluminum foil-paper laminate, aluminum foil, aluminum foilsealed with wax, and heat-sealed polyethylene. This feature of theinvention will be described more fully hereinafter with reference toFIG. 6.

EXAMPLE NO. 2

FIG. 2 shows a zinc-oxide-in-resin-binder xerographic sheet 20 which hasbeen negatively charged and reflex exposed through a right-readingnegative to provide an electrostatic image 21 thereon. The xerographicsheet 20` is brought into contact with a clay-coated paper receivingsheet 22 between which sheets a bead 28 of liquid developer isintroduced. About 10 ml. of bead of liquid developer was used. It wasmade by dispersing 1.0 g. of black lithographic ink (Sleight andHellmuth Tri Dim B) in 100 ml. of cyclohexane. The two sheets arebrought into contact by means of two conductive rollers 14 and 16. Theroller 14 behind the receiving sheet 22 is grounded and the roller 16behind the zinc oxide resin sheet 20 is held at 700 volt positive withrespect to ground. The liquid developer described above provides tonerparticles having a negative charge. As the xerographic sheet 20 and thereceiving sheet 22 pass between the rollers 14 and 16, the tonerparticles are electrically attracted to the uncharged areas of thexerographic sheet 20 and are then transferred to the receiving sheet 22,as shown by the arrows 25. A right-reading positive print is thusproduced on the receiving sheet 22. Although the theory of thisembodiment is not completely understood, we believe this to be aphysical, rather than an electrical, transfer of the toner particles.

EXAMPLE NO. 3

A zinc-oxide-in-resin-binder xerographic sheet 30 has been negativelycharged and projection exposed through a right-reading positivetransparency to produce an electrostatic image 31 thereon. Thexerographic sheet 30 is brought into contact with a clay-coated paperreceiving sheet 32 by means of a pair of conductive rollers 14 and 16. Abead 38 of liquid developer is positioned between the sheets as shown inFIG. 3. About 10 ml. of liquid developer containing positively chargedtoner particles is used. The rollers 14 and 16 are grounded. Apositivepolarity electrostatic image 33 is induced on the receivingsheet 32. As the xerographic sheet 30 and the receiving sheet 32 passbetween the rollers 14 and 16, the toner particles are attracted to theelectrostatic image 31, as shown by the arrows 35. A right-readingpositive print is produced on the xerographic sheet 30. The developer ismade according to the following procedure:

Ten grams of Amberlac D-96 (Rohm and Haas), a modied maleic anhydriderosin resin, were dissolved in 10 g. of Solvesso 100, the composition ofwhich is given in U.S. Pat. No. 2,899,335, by heating the mixture atelevated temperature. Ten grams of Nigrosine, Spirit Iet (GeneralAniline and Film) and 20 ml. of additional Solvesso solvent were addedto the resin solution. After 65 hours of milling in a micro mill, 25 ml.of Solvesso `was added and the mixture milled further for 36 hours.

Fifteen rnl. of Solvesso solvent, used to rinse out the mill, was addedto the liquid developer.

EXAMPLE NO. 4

FIG. 4 shows a negative-positive process in which azinc-oxide-in-resin-binder xerographic sheet 40` was negatively chargedand projection exposed through a rightreading negative transparency toproduce the electrostatic image 41 thereon. The xerographic sheet 40 wasbrought into contact with a clay-coated paper receiving sheet 42 bymeans of two conductive rollers 14 and 16. The roller 14 behind thereceiving sheet 42 is grounded and the roller 16 behind the xerographicsheet 40 is biased to 120 volt positive with respect to ground. A bead48 of liquid developer is positioned between the two sheets as shown inFIG. 4. The liquid developer is provided with negatively charged tonerparticles. About l ml. of liquid developer is used and is made bydispersing 0.1 g. of Sherwin William Solefast green negatively chargedtoner particles in 100 ml. of cyclohexane. As the sheets 40 and 42 arepassed between the rollers 14 and 16, the toner particles are attractedto the uncharged areas of the xerographic sheet 40, and to the inducedpositive electrostatic image 43 on the receiving sheet 42, asindicatedby the arrows 45. A positive right-reading print is produced onthe xerographic sheet 40 and a wring-reading negative print is producedon the receiving sheet 42.

EXAMPLE NO. 5

FIG. 5 shows a simultaneous positive-positive development and transferprocess. A zinc-oxide-in-resin-binder xerographic sheet 50 has beennegatively charged and projection exposed through a wrong-readingpositive transparency to provide an electrostatic image 51 thereon. Areceiving sheet 52 is provided which carries a layer of a mixture ofstyrene-butadiene and silicone resins. The two sheets are brought intocontact by means of two rollers 14 and 16 as shown in FIG. 5. A bead 58of liquid developer containing positively charged toner particles wasintroduced between the two sheetsgAbout ml. of a liquid developercomprising 0.l g. of Sleight and Hellmuth 7048 cyan lithographic ink in100 ml. of cyclohexane was used. The cyclohexane solvent softens thestyrenebutadiene and silicone resin layer in the receiving sheet 52, butdoes not attack the styrene alkyd resin in the xerographic sheet 50. Asthe sheets 50 and 52 pass between the rollers 14 and 16, the tonerparticles are attracted to the negative electrostatic image 51, asindicated by the arrows 55. They are then physically transferred to thesoftened, tacky, resinous, receiving sheet 52, to yield a right-readingpositive print thereon.

In this embodiment of the invention the resin used in the receivingsheet S2 must be softened and rendered tacky by the cyclohexane or otherorganic solvent in the developer, whereas the resin in the zinc oxiderecording layer must be insoluble in the solvent. The receiving sheet 52used in this example was zinc oxide in binder coated on a suitablesubstrate. The binder was a mixture of a silicone resin andstyrene-butadiene resin, The proportions may range from 5:95 to 50:50.The

preferred ratio in the styrene-butadiene is 70:30%. The silicone is anorgano polysiloxane resin having the recurring moieties represented bythe structural formula:

all .it

wherein x is an integer from 6 to 40, and R is a methyl or phenylradical, so chosen that both radicals on any given silicon atom areidentical and the molar ratio of methyl to phenyl radicals varies from4:1 to 1:4. The Zinc oxide material, in this case, served as a filler togive proper tackiness in the receiving sheet 52, and thepigment-to-binder ratio was 4:1. The Zinc oxide xerographic layer 50contained a cross-linked styrenated alkyd resin, Styresol 4440, ReicholdChemicals, which is not attacked by cyclohexane.

FIG. 6 shows a pod 60 of liquid developer 62 attached to a sheet `64 ofelectrostatic printing material. The .term electrostatic printingmaterial is herein defined, for purposes of the present patentapplication, as including both an insulating sheet capable of storing anelectrostatic image and a transfer sheet of conductive material such aspaper, because the pod 60 can be attached to either an insulating sheetto be provided with an electrostatic image or to the cover sheet. Thepod 60 is used as an alternative to the bead of liquid developerdescribed above. The material of which the -pod is constructed must benon-absorptive and must rupture under pressure to release the liquiddeveloper 62. The sheet 64 to which the pod 60 is attached may be eitherthe electrostatic image-bearing sheet or the receiving sheet, both ofwhich are described above. In one embodiment the pod is given sufficientstrength so as not to rupture under` normal packing and handlingconditions. In this way the pod can be manufactured, attached to thesheet of electrostatic printing material, for example, by the use of anadhesive, packed, and stored for later use. Various types of podconstruction are possible. In one type, for example, one end of thesheet of electrostatic printing material is rolled back onto itself toform a liquid developer container, which is filled with liquid developerand sealed at the ends to provide an integral pod and sheetconstruction.

In all of the embodiments described above with reference to FIGS. 1-5,the rollers 14 and 1-6 can be re` placed by any other suitable means forapplying pressure to the xerographic sheet and the receiving sheet asthey are brought into contact. In some of the alternative arrangements,a roller is used in co-operation with a flat surface; in another device,two at surfaces are used in co-operation with means for pulling the twosheets therebetween. In all such systems, in order to produce prints ofhighest quality (e.g., minimum background) it is necessary thatsuflicient pressure be applied to the sheets to prevent any excessdeveloper from going past the point of contact. By excess is meant anyportion of the liquid developer other than those toner particles whichhave been electrically attracted to one or the other of the sheets. Thispressure is sufficient to ensure physical transfer of the tonerparticles, in those embodiments wherein such physical transfer is totake place. The bead of liquid developer is continually pushed or forcedahead of the line of contact. Development is complete at the line ofcontact of the sheets.

The sheet materials may be moved lbetween the pressure rollers by manualor mechanical rotation of the rollers to cause frictional engagementbetween the rollers and the sheet materials or by manual or automaticpulling of the sheets through the rollers.

Although the present invention is particularly useful with zinc oxide,other photoconductive materials can be used including vitreous selenium,and organic photoconductors, such as anthracene, triphenylamines,polyvinyl carbazoles, etc. The cover sheet or transfer sheet in thetransfer processes can be any type of paper, preferably non-absorptive,or any other conducting material, such as metal foil 'and the like. Theliquid developer, when used as a bead, is introduced between the sheetsfrom any suitable container such as, for example, a col lapsible tube.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. In a process for developing an electrostatic image on one surface ofan insulating sheet and simultaneously reproducing said electrostaticimage as a positive rightreading image on a facing surface of a coversheet, the steps of forming a line of contact transversely of saidsheets and at which said sheets are pressed into engagement, positioninga liquid developer comprising a liquid carrier and charged toneparticles suspended therein which have a polarity of charge the same assaid electrostatic image between said sheets at the line of contact,moving said sheets as a unit relative to said line of contact tosimultaneously wipe said liquid developer across said surfaces whileholding said cover sheet and the outside surface of said insulatingsheet at electrical ground potential, whereby an electrostatic image isinduced on said cover sheet which has a polarity opposite to that onsaid insulating sheet, maintaining sufficient pressure on said sheetswhile bing moved to prevent any substantial amount of said carrier frombeing left on said surfaces while said toner particles are attracted toand deposited on said induced electrostatic image, and separating saidsheets.

2. The process according to claim 1 wherein said cover sheet is held atelectric ground potential and the outside surface of said insulatingsheet is held at a bias potential of the polarity opposite to that ofsaid electrostatic image, whereby said toner particles are electricallyattracted to the non-image areas on said insulating sheet and arephysically transferred to said cover sheet at said line of contact.

3. The process according to claim 1 wherein said toner particles have apolarity of charge opposite to that of said electrostatic image, wherebyan electrostatic image of the same polarity as said toner particles isinduced on said cover sheet and said toner particles are attracted toand deposited on said electrostatic image on said insulating sheet atsaid line of contact.

4. The process according to claim 1 wherein said cover sheet is held atelectrical ground potential and the outside surface of said insulatingsheet is held at a bias potential of a polarity opposite to that of saidelectrostatic image, whereby an image of a polarity opposite to that ofsaid electrostatic image is induced on said cover sheet and said tonerparticles are attracted to and deposited on said induced image and arealso attracted to and deposited on the non-image areas of saidinsulating sheet at said line of contact.

5. The process according to claim 1 wherein said cover sheet is providedwith a resin layer which is softened and rendered tacky by said liquiddeveloper, and said toner particles have a polarity of charge oppositeto that of said electrostatic image, whereby said toner particles areelectrically attracted to said electrostatic image and are thenphysically transferred to said tacky receiving sheet at said line ofcontact.

6. The method of forming on an image receiving web a visual record of alatent electrostatic image on an image support member comprising placingan individual droplet of developer comprising particulate electricallycharged toner suspended in a non-conductive liquid carrier on said Crtimage support member, simultaneously establishing a line of intimatephysical contact between successive portions of said image receiving weband said image support member and advancing said line, said developeradvancing in front of said line of intimate physical contact and betweensaid image receiving web and said image support member to deposit saidtoner particles on said image receiving web in image configuration atsaid line of intimate physical contact, and separating said web fromsaid image support member bearing a developed image.

7. The method according to claim 6 wherein said particulate tonercomprises a solution of resin in a solvent therefor and said liquidcarrier comprises a non-polar organic liquid.

8. The method according to claim 6 wherein said particulate tonecomprises a solution of resin in a solvent therefor and including theadditional step of fixing said tone particles deposited on said imagereceiving web by eliminating the solvent therefrom.

9. The method of depositing toner particles on an image receiving web inconformity with a latent electrostatic image on an image support membercomprising placing an individual droplet of developer comprisingelectrically charged toner particles suspended in a non-conductiveliquid carrier onto said support member, bringing successive portions ofsaid web into intimate contact with successive portions of said supportmember by rolling a cylindrical roller across said web andsimultaneously advancing said developer before the line of contactbetween said web and Said support member, and separating said web fromsaid image support member.

10. The method according to claim 9 wherein said roller is electricallyconductive.

11. The method according to claim 9 wherein said roller is electricallyconductive and an electrical bias is applied to said roller.

12. A method for forming on an image receiving web a visual record of alatent electrostatic image on an image support member comprisingadvancing developer comprising electrically charged toner particlessuspended in a non-conductive liquid carrier across said support memberby establishing a line of intimate physical contact between successiveportions of said web and said support member whereby toner particles areselectively deposited on said web in image configuration, and separatingsaid web from said support member.

13. A method for Xerographic image reproduction comprising applying anelectrostatic charge of one polarity to the surface of a Xerographicplate, exposing said plate to a pattern of light and shadow, placing anindividual droplet of developer comprising electrically chargedparticles suspended in a nonconductive liquid carrier on the said plate,establishing a line of intimate physical contact between successiveportions of said plate and an image receiving web and advancing saiddeveloper in front of said line of contact whereby printing of a visiblerecord of said latent electrostatic image is effected on said web, andseparating said web from said xerographic plate.

14. The method of developing a visible record of a latent electrostaticimage residing on an image support member comprising:

(a) establishing a line of intimate contact between a leading area of animage receiving web and the image support member at an individual beadof liquid developer on said image support member;

(b) advancing said line of intimate contact:

(l) to establish pressure contact between successive areas of said weband said image support member, and,

(2) to distribute and move said liquid developer across the surface ofsaid support member in advance of said line of intimate contact; and

(c) separating successive areas of said web from said support member;

9 wherein said liquid developer comprises electrically chargedparticulate toner suspended in a non-conductive liquid carrier.

References Cited UNITED STATES PATENTS 2,907,674 10/ 1959 Metcalfe etal. 117-37 3,063,859 11/1962 Heckscher 117-17.5 3,172,043 6/ 1965Metcalfe et al 96-1 10 3,234,019 2/1966 Hall 96-1.3 3,240,596 3/1966Medley et al. 96-1.4 3,247,825 4/1966 Johnson 118-637 CHARLES E. VANHORN, Primary Examiner U.S. C1. X.R.

